Method for testing the adhlsion of films of coating material



Dec. 2, 1947. D. M. WILLIAMS METHOD FOR TESTING THE ADHESION 0F FILMS 0F COATING MATERIAL Filed May 24, 1944 5 Sheets-Sheet 1 DAVID M.WILLIHMS 'FQ ATTORNEYS D. M. WILLIAMS 2,431,974

IETHOD FOR TESTING THE ADHESION OF FILMS OF COATING MATERIAL FilBd May 24, 1944 5 Sheets-Sheet 2 I/S-I F17. 7

, 255 INVENTOR.

DflvlD MzWILLIAMS K/ /////1////1////////////// /A'1 BY F1 a Q ATTORNEYs 1947- D. M. WILLIAMS 2,431,974

METHOD FOR TESTING THE ADHESION OF FILMS OF COATING MATERIAL Filed May 24, 1944 5 Sheets-Sheet 3 I 'INVENTOR. DPNLD M .WXLLIfXM S QMATTORNEYS Dgc. 2, 1947. D. M. WILLIAMS 2,431,974

METHOD FOR TESTING THE ADHESION OF FILMS 0F COATING MATERIAL Filed May 24, 1944 5 Sheets-Sheet 4 INVENTOR. a 1 www M .wlLL-mMs BY F1 7.13 r M ATTORNEYS ON OF FILMS 0F COATING IMPERIAL 5 Sheets-Shoot 5 1947- D. M. WILLIAMS us'r'aon won TESTING 'n-m ADHESI Filed Kay 24, 1944 INVENTOR DfiVID M.WILLI2 \MS ATTOR'N EYS scratches also use the Patented Dec. 2, 1947 METHOD FOR TESTING THE ADHISION OF FILMS OF COATING MATERIAL David M. Williams, Warrensville H assignor to The Arco Company,

Ohio

sights, Ohio, Cleveland,

Application May 24, 1944, serum. 531,132

10 Claims. 1

This invention relates to a method for testing the adhesion characteristics of surface films, particularly films of coating materials such as paints, lacquers, flowable resins and the like, adhering to solid surfaces. More particularly the present method for carrying out the invention pertains to a unique system for testing the adhesive quailties of films formed on metallic test pieces, whereby the lateral stress adhesion of the film is mechanically measured to ascertain the bond between the coating and the subsurface on which the coating is applied by applying a known standard stress to a decreasing area of adhesion interface until the bond is destroyed. In following this improved method of testing the adhesive qualities of coatingcompositions, a plurality of parallel or bisecting lines or grooves are formed through the coating film of decreasing spacing until the lateral stress placed on the intervening coating material between the lines or grooves displaces the material to thus determine the mechanical measure of the bond between the paint coating and the subsurface on which it is applied. In generating the grooves or lines through the film the displacement forcecreated in forming the lines or grooves is transmitted to the adhesion interface by the film itself, and in normal cases the cohesion of the film is\ greatly in excess of the adhesion properties thereof, and con- 's'equently the known lateral stress used in the grooving operation is a measure of the adhesion of the film. This application of force through the cohesion of the film. enhances the practical value of the present lateral stress adhesion methd and the data adduced from the operation of the apparatus, since scrapes, punctures or film structure to cause adhesion failures. The tensile .or pull determinations of adhesion have little practical value.

An object of the invention is to create a method of determining the adhesion factors of the film on a model test surface whereby standardizing information can be obtained and formulas varied to increase the adhesion qualities of the particular film. In carrying out the adhesion testin of the paint films and the like a paint film on a test piece is cut or grooved through the film to the metal base, in a plurality of cuts in paral-. lel or bisecting relation and ofdecreasing width between the cuts or grooves. In other words. the test lines formed through the film to the metal base are formed successively closer together, and if the film is not torn up between the lines a new series of grooves is made with a slightly closer spacing, and this is film between the grooves is displaced by reason of the lateral stress applied in forming the grooves and the adhesive bond between the paint coating and subsurface is destroyed. The cutting or grooving tool is moved through the film under a predetermined stress or weight which can be readily measured to obtain standardized data for various test pieces.

In the drawings Figs. 1 to 7 illustrate an adhesion testing machine where the operator manually selects the spacing of grooves on the test piece during the course of operation. In these figures:

Fig. 1 is a plan view of the apparatus showing the grooving operation;

Fig. 2 is a side elevational view of the apparatus shown in Fig. 1; v

Fig. 3 is an enlarged vertical section taken on lined-3 ofFig.2; 7 1V Fig. 4 is an enlarged detail view of the cutting or grooving tool;

Fig. 5 is an enlarged elevational view taken on line 5-5 of tool at the end of its return stroke and about to begin a cutting stroke;

Fig. 6 is an enlarged elevational view of the spacing or indexing wheel which is manually op-' erated for spacing the distances between the grooves cut by the tool;

Figs. '7 to 18, inclusive. show a modified form of the invention which is electrically controlled, wherein Fig. '1- is a detail-of the modified form of grooving tool and electriccircui't under control of the tool when the tool has penetrated throu gh the test" film and is in contact with the metal 1' Fig. 8 is an enlarged view or the modified cutting tool for forming the electrical contact with the test piece; v v

Fig. 9 is a'f'front elevational view of the modified or automatic form of machine in which each line or groove is automatically spaced from the adjacent precedins line;

Fig. 10 is a plan view of the apparatus shown on line 11- of Fig. 10 and showing the automatic and electrical spacing mechanism;

' .l'ig. 12 is a vertical section taken on line 12-42 of Fig. 11 of the automatic spacing device; Fig. 13 is a diagrammatical view showing the spacing device at the electrical circuit therefor;

Fig. 14 is a detail of the control elements of the automatic spacing device at the end of the spacing continued until the strip of 66 stroke; I

Fig. 1 and showing the cutting one point of its operation and v arms 45 each having Fig. 15 is a plan view showing a sample specimen with several series of grooves cut in the test plate and showing the series of grooves with different spacings therebetween;

Fig. 16 is an enlarged section taken on line I-Il of Fig. 15, showing the Grooves formed completely through the test film to the metal base: and.

Fig. 17 is a modifiedsroove formation where the test cuts bisect one another.

In the form of manually controlled apparatus shown in Figs. 1 to 7, inclusive, numeral I de able support I mounted for movement on spaced apart parallel rails I-iiJormed on thetop oi thelmachine base 9.

The ends oi the rail 1+1 are connected by cross pieces I'I.-,-II' through which a rotatable feed screw Ills iournalled. The feed screw I9 is threaded through a'threaded nut'or tube I secured to the under side'oi' the slidable test table support 'i'ior'moving the At the front of .the'machine the feed screw is is attached to and adapted to -herotated by a ratchet wheel v Limited rotary movement may hejfjgive'nfthe ratchet wheelj ifi'and associatedjeed screen-by engagement 'ofj the teeth -thereof :by the pressed pluneeri 9" carried in outer-end "of a pivoted lever '2! which is lournailed on the feed screwi i between-"the cross'iii'eiie 'ifi f'and the ratchet wheel I'Ii' Thus' -when the-plunger I9 is in engagement with the ratchet wheel I1 and the lever 'ls'movedclockwise the feed screw I3 rotated and the nut I9 is port 5 carryingrth'etesrtable'I will be moved along the rails 1- 1; Theamount of rotative movement. of the ratchet wheel" is controlled by the setting of a stop pin 23 which isadjustably positioned inthe' indexing segment 21, while retrograde movement is limited by fixed stop pin 29.

The test piece is preierably made up of a metal sheet 35 having a hardened film of paint or other coating material 31 thereon, and the test piece is is held in adjusted position by the oflset handle I having a pin 43 therein for engagement with the desired opening lii'formed in'the edge of theslidablesupport-lc-dz" As shown in Figs.'"1: and 2, the the machine is provided a vertical. section -,41iupporting a horizontal cros 49 ior holding a 59 having four spaced depending, tubular sections 9i through which the track rods 5| pass. Secured to the upper face of the slidable hori-- zontal plate 59 vertical arms 63 fitted with inwardly extended verse axle pin 13 on pivot arm 15 oscillates.

I1 having a handleit.

on the slidable su openings 25 formed in the,

ing arm I! passes through an opening 11 formed in the slidabie horizontal plate 09 and the opening is of such a size that it restricts movement of the vertical arm 15 through an angle of about 15'. An offset pin II is secured in the side of the arm 15 for engagement with the lower edge 99 of the "vertically pivoted plate 91. As seen in Fig. 5 the lower edge 09 01 the plate 61 is provided with an inclined portion 05 and an adjacent indented portion 87 so that when the arm 15 is in dotted line position the pin 9i does not contact the lower edge 93 01' the plate 61, but upon clockwise oscillation thereof the pin 9i will ride vonthe cam surface 95 as shown in the solid line position to lift the right end 01' plate 61.

r The tool holder comprises a cylinder 86 bolted to-the outer end oi the vertical pivot plate 91 and carries-therethrough a rotatable rod 81' having a socket 89 in the lower end thereof for the dein. position? by set screw tachable-insertion of a grooving tool 9| secured 93. The upper end of rod-81 is provided with the rotatable tool, holding a pinion 9.5 which-,-cooperateswith the endo! ring .pushrod I09 which with apain-ofi-extendina' A pair of depending spaced parallel arms H extend downwardly from the plane of the slidable plate 59 to form a holding means for which a vertically extendin This upwardly extendpin .II3 secured to the base II5.

159,11as will lie hereinafter; described. I The growing or cutting ltoolliis preferably provided with a conical. diamond tip 99, although other types oted through an anti-vibration bushing I01 to is plvotally connected to lower end embraces a pivot A follower II! 'is secured to an intermediate portion of the pitman I I I and rides within the groove N9 of the Rotative movement is given to a pitman II I, whose follower III carried around the cam groove II9 to reciprocate the push rod I09 and move the tool carriage 59back and forth across its plate 35. As shown in detail in Fig. 5 the cutting action of the tool 9i through the him 31 on the test plate 35 is accomplished push rod I09 a point through the test film carriage which provides for freeing the arm I! from the carriage at the cadet the cutting stroke and before the non-cutting return stroke is pro-.-

previously mentioned. Then lever is moved to the opposite side of the opening 11, whereupon the pin II rides up the cam surface ll formed on. the lower port of the plate It and raises the plate "on its pivot bolts 88, and thus during the return movement of the carriage the tool carried by the plate is lifted out of contact with the test piece. Further rotationof the cam plate III and its associated mechanism repeats the cycle just described.

The setting of the pin 23.0n the indexing plate 21 permits'the operator. to feed the test plate table I through the contact of the dog I9 with the ratchet teeth on wheel I1 to slide the plate slightly, whereupon as the tool ll is rec procated a furthercut is made in the material to be tested. Figs. 1 and 15 show a. test plate which hasbeen grooved with a series of test cuts I3I through the film 31 with each series of test cuts of lesser spacing from one another than the preceding series. This closing or reduction of the spacing rod It! moves the carriage to a tool has penetrated the film Q of the modified machine like parts of the manually operated machine of Figs.

. parts of the machine the tool holding cylinder between the several test grooves by decreasing the spacing between the cuts in each series is continued until the grooves are so close to one another that the lateral stress placed upon the film in-cutting the groove is sufficient to break the bond between the narrow strip of film and the model test surface, and inasmuch as the operator knows the weight placed on the tool he is able to determine, through listing the various variables present, the adhesive characteristics of the film. The enlarged view of a series of test grooves I3I as shown in Fig. 15, includes an illus tratlon of patches I33 between the closely positioned grooves from which the paint has been laterally displaced. It will be obvious that any suitable data can be charted-by the operator so as to give a basis for testing the various films of coating materials. In Fig. 16 there is shown a greatly enlarged cross-section of the form of grooves HI and intermediate film 31 made by the cutting tool'after it has penetrated the film and is in contact with the test surface 3!.

In initiating the first test groove I3I through the film 31 the tool point 99 may be moved across the test surface a number of times until the hard of the tool contacts the test plate or aninltial groove I3I having suihcient pressure to cut through the film 31 can be accomplished by increasing the pressure on the tool point by adjusting the slidable weight I03. As before stated, the

end of the hooked rod 91 moves the pinion 95- slightly near the end of each return stroke to rotate the tool shaft 81 a few degrees so that the life of the cutting tool 99 is prolonged. To pre-. vent chatter or undue vibration the cuttingposition of the tool is tilted slightly, generally 5 degrees from the perpendicular.

In the modified form of apparatus shown in Figs. '1 to 14, inclusive, the groove III are cut 31 and spread automatically without manual operation of the groove spacing ratchet wheel and feed .means. In these figures is made of dielectric and an insulating plate Iii-is placed under the test plate holder I31 on the table I see Fig. '1. The cutting tool holder 91 is preferably insulated by a dielectric washer In from the pinion while the holder 81 is connected by conductor III to one side of a. switch I43 which when closed completes a circuit with power line I45. The other line of the switch I43 is connected through conductor I41 with the conducting plate I31 underlying the metal test plate 31. Thus with switch I43 in closed position it is connectedthrough conductor I41 with the conducting plate I31 underlying the metal test plate 91. Thus with the switch I43 in closed position an electrical circuit is completed when the point of the all metal grooving tool I5I has cut through the test film 35 and contacts the plate 31, see Fig. '1. Continuity of the circuit is observed on a meter ill and as contact is made by the tip of the tool ISI with the metal plate and recorded on meter I58 two further circuits are completed. The first circuit includes the solenoid Iii placed in the line HI, I51, through the meter I53 and joined to the line I51 leading to the switch I, the other portion of the circuit includes the plate I35, and line I43, so that when contact is made by grooving tool IS 'I the solenoid I55 will be energized and the latch I59 pivoted a't IGI and biased by spring I83 will be drawn or released from latched position from finger I66 of pivoted brush holder I65. The circuit of he second solenoid I61 is controlled by contact rush I69 secured to pivoted brush holder I55 and connected to conductor I51. so that when contact brush I99 is in contact with c ontact strip "I connected to the solenoid I61 the circuit from the solenoid I61 is completed .through conductor I13 joined to line I43. This portion of the apparatus is for the purpose of automatically rotating feed screws I11 to advance the test table I whereby successive test grooves are made in the test panel.

In modified views, Figs. Ho 14, inclusive, a

connecting rod I9! is attached at one end to the reciprocating arm III of the drive unit while the opposite end-is attached through stud I 91 to a vertical arcuate segment I89 pivoted on the rear extension I9I of the feed screw I11. The

solenoids I55 and IE1 are also secured to the segment I" and move therewith as does the dog I93 pivoted on stud I95 fastened to the front face of the segment.

Also plvotally connected to the end portion of feed screw shaft I11 is a vertically extending arm I99 having an arcuately formed axially projecting segment 2M which normally lies over' the upper portion of the ratchet wheel 203 that is at;- tached by a set screwto the feed screw shaft. In spaced relation to the vertically extending arm 1 to '1 have been similarly identified. The driving unit commie-- the adhesion of the film :1 cannot prop- 05. This unit of the device is not regularly connected to the end portion I9I of the feed shaft but is pivotally mounted thereon. As seen in Figs. 13 and 14 the axially extending arcuate shield 28I overlies the teeth on the ratchet wheel 208 and dog I93 from engagement 89 by means of the connecting rod I85 the dog I93 passes over the end of the shield MI and engages the teeth of the ratchet wheel to move it in a clockwise direction until and engage 3 Movement of the collar 22I is restrained by a friction brake 225 sebase frame of engages the axial extension 228. Thus if during the ilrst part of the ratchetor power stroke the solenoid I55 is energized the brush holder I88 is free to rotate slightly being upper stop pins 227 lying on either side of the extension 229 thereof. Since movement of the collar MI is restrained by the brake any movement of the segment I89 to the right will cause the brush holder I65 to tend to revolve clockwise and complete the electric circuit between the electric contact arms I89 and I II. However,

I56 and I6! and all other ov rthe machine and destroyed limited by the two if current is flow near the end or Ill and thus allowed dog I98 from theratchet deenergized and the spring 2I ing end I93 of the d 8 ing through solenoid I58 at or the cutting stroke then a feed arcuate contact to be withdrawn In use this automatic feeding mechanism permits the operator to under the constant regulation oi the operator by the positioning a If desired, ang

I claim: 1. The method of the film index of the of the handle 201. ular bisecting grooves may be of testing the adhesive characof coating material applied to a ises cessive paths at which the film is sheared from its base, as an index of the adhesive characteristics of the him.

4. The method predetermined stress is applied to as defined in claim 3 wherein a 'the two successive grooves the said film to its base in generally v shaped grooves whereby displacement stress effective laterally of the film is generated, forming said grooves in successively closer parallel paths until portions of the film between successive grooves are displaced by destruction of their adhesive bond and utilizing the width of the space between where the film is displaced from the base as an index of the adherent properties of the film.

7. The method of testing the adhesive characteristics of a film of coating material applied to a base which comprises cutting said film to the base and applying lateral stress along successively closer paths until the adhesion bond between the film and the base is destroyed and utilizing the width of the space between two successive paths at which the film is sheared from its base, as an index of the adhesive characteristics of the film.

8. The method as defined in claim 7 wherein a predetermined stress is applied to the decreasing area of the adhesion interface lying between parallel spaced grooves out through the said film.

9. The method as defined in claim 7 wherein a predetermined stress is applied to the decreasing area of the adhesion interface lying between angular bisecting grooves cut through the said film.

10'. The method of determining the adhesive properties of a film of coating material on a base which comprises cutting uniform parallel grooves through said film of progressively varying spacing, applying substantially parallel to the adhesion interface a localized constant predetermined dynamic stress to the progressively changing areas of the adhesion interface between the cut grooves and within the zone of influence of said stress, until a change occurs in on the bond between the film areas and the base, and utilizing the efiective area where the change occurs as an index of the adhesive properties of the film.

' DAVID M. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

the effect of said stress 

